I should start by saying that I don't know the answer to your question (I don't base my training plans on lactate numbers). However, reading Steve Magness' blog might help you get closer to what you're looking for.
http://www.scienceofrunning.com/2007/01/lactate-thresholdwhat-heck-is-it.html
From my experience, you need to be very careful when taking measurements. Some coaches I've talked to don't seem to understand what it is they're measuring: they don't understand the variables that affect the measurements and their sensitivities.
Furthermore, in the same way that elite distance runners and cyclists have widely varying VO2 max numbers (often the best endurance athletes do not have the best VO2 numbers) different rowers' bodies react differently to stress.
As you'll gather, I'm a bit of a sceptic when it comes to driving training sessions using lactate measurements. If you manage to get through all this and come out the other side with an answer, do let me know! I'm always open to being proven wrong!
Good luck,
TC